This invention relates to a surgical stapler for implanting staples into the skin and/or tissue for wound closure after a traumatic injury or a purposeful incision in a surgical procedure.
It has become a preferred procedure to use staples for wound closure rather than thread or filament sutures. Surgeons choose staples because of the speed with which an incision can be closed as compared with the time consuming placing and tying of thread or filament sutures.
Many surgical staplers have been designed with various features to improve the profile of the stapler to increase visibility for the surgeon during the placing of the staples and to improve the reliability of the stapler with respect to serial delivery of contained staples without jamming. See, for example, U.S. Pat. Nos. 4,014,492, 4,109,844, 4,179,057, 4,202,480, 4,256,251, 4,375,866, 4,407,286, 4,489,875 and 4,527,725. The above patents describe staplers using preformed staples without a forming anvil, staplers having a movable or retractable forming anvil as well as a wide variety of feeding mechanisms to deliver each staple to the delivery point where the staple is deformed during implantation into the skin and/or tissue.
In an effort to improve visibility for the surgeon, the angle formed between the bottom of a stapler and the skin or tissue surfaces being joined has been increased in prior art staplers with the result that it has become increasingly difficult to retain jam-free delivery of the staples, particularly in those staplers where the staples are sorted on a covered retaining track or rail and fed serially thereon to the forming jaws and forming anvil. The increased angle of the stack of staples sorted in such a feeding mechanism of a stapler and the pressure of the biasing means, e.g., a spring biased pusher, tend to cause the stack of staples to buckle and jam the stapler, i.e., a following staple tends to push under a leading staple like a wedge and cause a jam in the feeding mechanism. This problem was at least partially overcome by the teachings of U.S. Pat. No. 4,662,555 which discloses a shuttle in association with the rail as a movable staple retaining cover which moves in the same direction and at the same time as the staples being fed along the rail. This structure provides a reliable surgical stapler in which staples are not likely to jam the staple feed mechanism.
In U.S. Pat. No. 4,662,555 a cantilever spring is disclosed as part of the rail. Its purpose is to support the next staple to be deformed before deformation. A problem has arisen where occasionally the staple will be deformed around the spring 48 which is in the center of the end of the rail. This causes the staple deformed into the tissue to be stuck in the stapler. When the stapler is withdrawn, it tugs at the tissue.